Summary: Ebola virus (EBO) is a "Category A" BT agent that causes hemorrhagic fever and results in a high mortality rate. Research in EBO has been hampered by the strict biosafety containment procedures required for handling the infectious agent. EV cell entry is mediated by the interaction of a cellular receptor with the GP1 subunit of the viral envelope. Studies using recombinant EBO envelope are feasible in BL-2 containment facilities at CBER. Although little is known about the mechanism of cell entry of EBO, the folate receptor (FR ) and the dendritic cell-specific ICAM-3 grabbing non-integrin receptor CD209 (DC-SIGN) and its homolog L-SIGN have recently been identified as cofactors for cellular entry of EV in certain cell types. It is likely that other not yet identified cellular receptors play a role in EBO cell entry. To identify cellular receptors for EBO and develop biologics capable of preventing cell entry, we will overexpress the EBO envelope in insect cells and CHO cells. Purified recombinant EBO envelope will be used to screen human cDNA libraries using an expression cloning strategy to identify novel ligans. Soluble forms of DC-SIGN, L-SIGN, FR , and newly identified ligands will be produced to determine whether they could block binding of the EBO envelope to cells. Humanized monoclonal antibodies against the recombinant EV envelope will be produced using antibody displayed phage libraries. Soluble receptors and monoclonal antibodies that block binding of EBO glycoprotein to cells will be further characterized and evaluated as potential treatment for EBO infection.